through some hole in this tunnel. They never came out the main
entrance."

Tom held to this view in spite of the fact that nearly every one else
believed the contrary--that the men had left by the tunnel mouth, near
which Tom happened to be alone at the time.

Now, left to himself, with merely nominal duties, and so disguised that
none of the workmen would know him for the trim young inventor who
oversaw the preparing of the blast charges, Tom Swift walked to and
fro, looking for some carefully hidden passage or shaft by means of
which the men had got away.

"For it must be well hidden to have escaped observation so long," Tom
decided. "And it must be a natural shaft, or hole, for we are boring
into native rock, and it isn't likely that these Indians ever tried to
make a tunnel here. There must be some natural fissure communicating
with the outside of the mountain, in a place where no one would see the
men coming out."

But though Tom believed this it was another matter to demonstrate his
belief. In the intervals of seeing that the natives properly loaded the
dump cars, and removed as much of the debris as possible, Tom looked
carefully along the walls and roof of the tunnel thus far excavated.

There were cracks and fissures, it is true, but they were all
superficial ones, as Tom ascertained by poking a long pole up into them.

"No getting out that way," he said, as he met with failure after
failure.

Once, while thus engaged, he saw Serato, the Indian foreman looking
narrowly at him, and Serato said something in his own language which
Tom could not understand. But just then along came Tim Sullivan, who,
grasping the situation, exclaimed:

"Thot's all roight, now, Serri, me lad!" for thus he contracted the
Indian's name. "Thot's a new helper I have, a broth of a bye, an' yez
kin kape yer hands off him. He's takin' orders from me!"

"Um!" grunted the Indian. "Wha for he fish in tunnel roof?" for Tom's
pole was one like those the Indians used when, on off days, they
emulated Izaak Walton.

"Fishin' is it!" exclaimed Tim. "Begorra 'tis flyin' fish he's after
I'm thinkin'. Lave him alone though, Serri! I'm his boss!"

"Um!" grunted the Indian again, as he moved off into the farther
darkness.

"Be careful, Tom," whispered the Irishman, when the native had gone.
"These black imps is mighty suspicious. Maybe thot fellah had a hand in
th' disappearances hisself."

"Maybe," admitted Tom. "He may get a perc